We will develop a novel approach to detecting transgene activity in tumors based on proton MRI of enzyme activated reporter molecules. Specifically, we will synthesize, evaluate, optimize, and apply novel agents to detect (3-galactosidase activity generated by the lacZ gene. Gene therapy holds great promise for treatment of cancer. However, major problems involve assessing delivery to target tissue, the uniformity (versus heterogeneity) of bio distribution and determining whether the genes are expressed. We propose a novel approach for evaluating gene expression using MRI. This research draws on foundations in optical detection of reporter genes, specifically P- galactosidase from the lacZ gene. Recently, 3,4-cyclohexenoesculetin-p-galactopyranoside, marketed commercially as S-Gal(tm), has been shown to generate an intense black color as a precipitate upon activation by p-gal in the presence of Fe3+ ions. This prompted us to consider the paramagnetic properties of the precipitate as a potential 1H MRI contrast agent. Preliminary studies have demonstrated feasibility and we now wish to translate and develop the concept to tumor cells for detection in vivo.
Specific aim 1 will explore the utility of S-gal, with investigations to optimize and validate the technique. MRI parameters will be varied to maximize contrast with appropriate spatial and temporal resolution. Agent administration will be evaluated to maximize contrast and minimize toxicity.
Specific aim 2 will focus on translation to tumors in living mice. MRI will be validated by comparison with optical methods in vivo and traditional methods such as histology and RT-PCR.
Specific aim 3 focuses on the synthesis and development of alternate optimized substrates. We believe this approach can both become a valuable tool for detecting p-gal activity in vivo and serve as a proof of principle for a novel platform technology adaptable to other reporter genes and endogenous enzymes such as proteases. ? ? ?
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| Gulaka, Praveen K; Yu, Jian-Xin; Liu, Li et al. (2013) Novel S-Gal(®) analogs as (1)H MRI reporters for in vivo detection of ?-galactosidase. Magn Reson Imaging 31:1006-11 |
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| Yu, Jian-Xin; Gulaka, Praveen K; Liu, Li et al. (2012) Novel Fe(3+)-Based (1)H MRI ?-Galactosidase Reporter Molecules** Chempluschem 77:370-378 |
| Liu, Li; Mason, Ralph P (2010) Imaging beta-galactosidase activity in human tumor xenografts and transgenic mice using a chemiluminescent substrate. PLoS One 5:e12024 |
| Cui, Weina; Liu, Li; Kodibagkar, Vikram D et al. (2010) S-Gal, a novel 1H MRI reporter for beta-galactosidase. Magn Reson Med 64:65-71 |
